Cryonics Magazine, August, 2013
Why Reversible Cryopreservation Matters
[The following is a text adaptation of a PowerPoint presentation given on Sunday, May 12, 2013 at the Resuscitation and Reintegration of Cryonics Patients Symposium in Portland, Oregon.]
Let’s start with the following definition of cryonics:
“Cryonics is the stabilization of critically ill patients at ultra-low temperatures to allow resuscitation in the future.”
As you can see, nothing in this definition says that repair is an intrinsic feature of cryonics. But is this a reasonable perspective? Let’s think about a number of aspects of cryonics that could be classified as “repair.”
• Critically ill patients are sick and will need medical treatment in the future.
• Most cryonics patients will require
• The cryopreservation process itself causes (irreversible) damage.
Yes, cryonics patients will require a second look at their condition by a future doctor who will have more advanced medical technologies at his/her disposal. This could conceivably be called “repair.” Most cryonics patients will also require rejuvenation biotechnologies. After all, it makes little sense to cure the patient’s disease but leave him/her in a fragile, debilitated state. This could be called “repair” too, in particular if you believe that aging is the progressive accumulation of damage. The repair that I want to discuss here is repair of the damage that is associated with the cryopreservation process itself. If we can eliminate this kind of damage, and the associated requirement of repair in the future, we will make the idea of cryonics a whole lot more attractive. What would be the advantages of being able to offer such “cryonics without repair?”
Perhaps the most obvious advantage is that cryonics could not be dismissed solely by pointing to the (irreversible) damage caused by the cryopreservation process itself. In essence, such a form of cryonics would be akin to putting a critically ill patient in a state of true suspended animation. This would strengthen the legal position of cryonics patients because a decision to abandon a patient in such a condition would be more akin to murder (or at least serious neglect). Another advantage would be that the absence of cryopreservation damage would increase the likelihood of the patient being restored to good health in the future. Less damage is also likely to translate into lower costs, too, and it is rather obvious that such an advantage can mean more security for the patient. Reversible cryopreservation may also lead to earlier treatment and resuscitation attempts, which may reduce challenges associated with re-integration. Cryonics without repair also matters in the here-and-now. Without the goal of reversible cryopreservation there are no objective, empirical criteria to evaluate the quality of care in a cryonics case. Last, but not least, we should do no harm. Allowing unnecessary injury of the patient because future advanced technologies should be able to fix it is a morally suspect gamble with a person’s life.
That is an impressive list of arguments in favor of offering reversible human cryopreservation. Now let’s try to be more specific about what cryonics without repair means. Clearly, the condition of the patient should not worsen relative to the critical condition the patient was in at the time of pronouncement of legal death. In fact, a rarely recognized possibility in a good cryonics case is that it might even be feasible to slightly improve the condition of the patient through the administration of cerebroprotective medications and washing out the blood, provided these procedures do not restore spontaneous circulation and consciousness, of course. A common perspective at Alcor to look at the objective of stabilization procedures is to say that these procedures should be aimed at maintaining viability of the patient by contemporary criteria. In the past I have characterized this objective as securing viability of the brain, but I think it would be better to aim for complete viability of the body unless there is a clear trade-off between viability of the brain (the most important organ in cryonics) and the rest of the body. Ultimately, though, we do not just want to be able to reverse the stabilization procedures but all cryonics procedures.
Before we walk through basic cryonics procedures to identify obvious and notso- obvious opportunities for cryonics procedures to produce additional damage, let’s look at circumstances in which the patient suffers additional damage that cannot be attributed to the cryonics organization. The most obvious situation is where there is a long delay between pronouncement of legal death and the start of cryonics procedures because hours go by before the patient is discovered or hospital administrators do not allow immediate access. It is important to recognize that the goal of maintaining viability can be defeated before we even start our procedures. Critics of cryonics often talk about compromising circumstances as if they are intrinsic aspects of cryonics instead of the result of tragic but avoidable events or hostile authorities. Reversible cryopreservation is only possible if the cryonics organization is notified in time and receives good cooperation from hospital administrators and other authorities.
The first real opportunity for a cryonics organization to “screw up” is to allow substantial periods of warm and cold ischemia. This can happen in a number of ways including, but not limited to, not restoring adequate circulation, inadequate ventilation, allowing blood pressure and cerebral perfusion to drop (restoring blood pressure does not guarantee good cerebral blood flow), suboptimal induction of hypothermia, or conducting surgery at high temperatures without metabolic support. In ideal circumstances a cryonics stabilization is conducted so that suboptimal results in one of these areas are offset by gains in the other protocols.
If a cryonics organization is able to provide metabolic support and rapidly cool down the patient to close to the freezing point of water the next challenges involve the cryopreservation process. The best known form of damage here is, of course, ice damage. While today’s vitrification agents are formulated to inhibit ice formation at realistic cooling rates, there are still a number of things that can go wrong. The distribution of cryoprotectant in the brain can be incomplete as a result of surgical errors or flaws during cryoprotective perfusion (e.g., vessels not properly cannulated, extremely low or high pressures, pumping air, etc.) The cryoprotectant can also be introduced at temperatures that are too warm or introduced too rapidly to allow the cells to maintain volume in an acceptable range. Even if none of these mistakes are made, we run into other challenges that cryonics organizations cannot successfully overcome yet.
Successful vitrification requires the use of high concentrations of organic solutes (such as DMSO and formamide) and non-penetrating polymers. While much progress has been made by cryobiology researchers Gregory Fahy and Brian Wowk to formulate solutions with low toxicity, and such solutions have been shown to successfully cryopreserve brain slices, our current understanding is that it is not likely that the brain of a cryonics patient remains spontaneously viable after being equilibrated with these agents. This is partly because the “blood brain barrier” leads to a situation in which solutes naturally present in the brain become concentrated during cryoprotective perfusion (dehydration) as discussed in the next paragraph. This causes cells inside whole brains to be cryoprotected by a mixture of natural solutes and some components of the perfused cryoprotectant solution rather than just the carefully-formulated cryoprotectant solution. Sometimes natural is not good.
It is sometimes said that eliminating cryoprotectant toxicity is the “holy grail” of cryonics research. While there is good empirical evidence to suggest that despite this toxicity good ultrastructure of the brain is still possible, true reversible human cryopreservation without reliance on sophisticated repair will require cryoprotectants with much lower toxicity. The need for less toxic cryoprotectants is especially tied into the problem of achieving concurrent and adequate distribution of cryoprotectant to all parts of the body that are vulnerable to freezing injury, which requires many hours of perfusion. In addition to cryoprotectant toxicity there are a number of other poorly-understood phenomena that could frustrate the ideal of cryonics without repair such as “chilling injury” and “thermal shock.”
An interesting form of injury that is not well known by the general public but that triggers a lot of discussion among cryonics researchers is dehydration of the brain. Without exception, a wellconducted cryopreservation of the brain with present technology produces severe shrinking. In fact, this shrinkage, and the corresponding increase in concentration of salts and proteins naturally present in the brain, appears to be a key mechanism by which whole brains vitrify despite limited permeability to perfused cryoprotectants. Evidence of substantial dehydration (obtainable by direct inspection of the brain inside the skull or via CT scans) is often considered an indicator of good care in cryonics. Of course, this leaves the question unanswered whether such a degree of dehydration is compatible with viability of the brain. Yuri Pichugin, the researcher who developed the Cryonics Institute’s current vitrification agent, VM-1, considered such extreme cerebral dehydration an obstacle to restoring viability after vitrification and identified a number of blood brain barrier modifiers that allowed him to recover brain slices after whole brain cryoprotective perfusion with improved viability. Whether such agents are of benefit or actually harmful is still an open research question.
Even if we could cryopreserve a human being without ice formation, toxicity, chilling injury, or other forms of injury associated with cryoprotection, there is still one remaining obstacle for reversible cryopreservation: fracturing caused by thermal stress. While fracturing has been recognized as a problem and observed as an empirical phenomenon in patients as far back as the early 1980s, this form of injury has pushed itself to center stage (together with cryoprotectant toxicity and cerebral dehydration) since cryonics organizations started using vitrification agents aimed at eliminating ice formation altogether. If ice formation is eliminated, fracturing is the only mechanical form of damage left. While the significance of fracturing damage is sometimes downplayed by molecular nanotechnology experts, and fracturing at cryogenic temperatures doesn’t result in actual fragmentation, letting a human brain form fractures is not what most people would consider appropriate treatment of a critically ill patient.
What is striking, however, is how little we actually know about fracturing in cryonics patients. Fracturing has been observed in patients that were cryopreserved with (relatively) low concentrations of cryoprotectants. Such protocols produced ice formation and we should therefore not be surprised about observing cracking in those patients. Even in patients who have been cryopreserved using modern vitrification agents acoustic fracturing events (which may or may not correspond with actual fractures) have been detected above the glass transition temperature (Tg) of the pure vitrification solution. But even these observations have little relevance to the question of what we should expect in a good case. Many cryonics patients are perfused under sub-optimal conditions due to delays after clinical death. It is therefore likely that many of these fracturing events, if real, can be attributed to ischemia-induced perfusion impairment and ice formation. And that cooling frozen tissues to very low temperatures can cause fracturing is something we already know.
There are some encouraging preliminary research results suggesting that under ideal circumstances (i.e., good equilibration, controlled cooling) fracturing is not as serious a problem as it has been made out to be. The current practice of long term care at liquid nitrogen temperature may not be salvaged by such observations, but the intermediate temperature storage (ITS) systems that have been developed might be sufficient to eliminate this problem under good conditions at temperatures not too far below Tg. A related intriguing question is what the effect of severe cerebral dehydration is on the occurrence and frequency of fractures in the brain.
Let’s say that one agrees with the objective of “cryonics without repair” (or very limited repair), and the identification of the biggest scientific and technical obstacles to achieve this. What should our research and clinical objectives be? For starters, cryonics organizations should continue to cultivate an interest in personal alarm systems and securing good legal and logistical cooperation with providers of medical care. One technical development that deserves to be introduced is “field vitrification.” Strictly speaking, the phrase is a misnomer because we are not really talking about the patient being vitrified in a remote location; it is the cryoprotective perfusion part of the procedure that is done prior to transport to Alcor (in remote cases). Evidence from at least three labs indicates that perfusing the patient in the field with a vitrification solution and shipping on dry ice is safe, practical, and superior to blood substitution in most scenarios. While remote blood substitution (“washout”) is clearly demonstrated to be better than shipping the patient without removing the blood, it is not likely that hypothermic organ preservation solutions capable of keeping the brain viable for longer than 24 hours, and capable of inhibiting whole body edema, will be developed any time soon. Field vitrification is simply the next logical development in high-quality evidence-based cryonics. Other important improvements include better cooling efficiency (e.g., using cyclic cold lung lavage), improved cardiopulmonary support protocols, a renewed emphasis on monitoring during casework, and the introduction of intermediate temperature storage.
The most formidable challenge will be to develop what I call “brain-friendly” cryoprotectants. What needs to be accomplished? These agents should have no, or tolerable, toxicity, eliminate chilling injury and other poorly-understood forms of cryopreservation injury, allow safe and fracture-free storage at intermediate temperatures, and allow cryoprotective perfusion with greater penetration of agents into brain tissue with less dehydration so that results in whole brains can more closely match the high viabilities now obtainable in brain slices.
At my own company, Advanced Neural Biosciences, we have successfully developed a rat EEG model to screen for such brain-friendly cryoprotectants. As I write up this presentation, we have been successful in recovering integrated whole brain electrical activity after hypothermic circulatory arrest at 0° Celsius. Our next objectives are to recover EEG activity in the brain after cooling to subzero temperatures and to understand the relationship between cryoprotectants, the blood brain barrier, dehydration, and viability. It is too early to report any significant findings yet, but one thing that has become quite clear to us is that adequate ventilation during cool down is essential to recovery of whole brain activity. This is rather important because cryonics organizations have not been that concerned about meeting the brain’s demand for oxygen during stabilization, and during blood washout and blood substitution in particular. No doubt, if we continue this research we will learn other things that have direct relevance to the practice of cryonics.
The whole brain cryopreservation research project has been made possible by the generous support of the Life Extension Foundation. The author also wishes to thank the Immortalist Society, Cryonics Institute, Alcor, LongeCity, 21st Century Medicine, Alan Mole, York Porter, Jordan Sparks, David Ettinger, Ben Best, Mark Plus, Peter Gouras, James Clement, Luke Parrish, and John Bull for additional support.